Don't worry about IS draining your battery. I recently shot a 90 minute figure skating event with 70-200 f2.8L II on a 7D using just the stock battery (no grip). 2,000 images later, and my thumb parked on the back focus button for most of the 90 minutes, the battery was at 76% after the shoot.

Chuck Westfall says the AF potentially works faster and more accurately with IS on.

"You would be better off with the IS version for skiing photos, for a reason that might not be obvious at first glance. Although chances are good that you'll be using a shutter speed so fast that the IS system has no effect, use of IS will present a steadier image to the camera's AF detection system. Thus, if you're using predictive focus, the IS system may provide better data for the AF system to base its calculations on. However, if you're just zone focusing manually and waiting for the subject to pass through the area you've preselected, then you might as well shut off the IS function and save some battery power."

Again, IS on does not slow down AF, indeed it might be beneficial to AF performance even when shooting at shutter speeds that don't necessitate it. If you don't agree go tell Chuck

On the battery usage, I have gone through two LP-E4's in a day shooting surfing with IS on, but never come close to that without using IS on a days shoot.

IS on the bigger lenses chews battery, esp in the heat/cold. I can say now I have spent more on batteries and chargers shooting skiing/snowboarding (I keep 6 spares) then I thought I would have to. I have tried Chuck's method and can honestly vouch for it in the park and half pipe (lots of steady fluid motion). It does not work so well for kayaking and kiteboarding IMO. Only did about a month of work with those crazy people though so did not have a ton of time to test it.

IS is remarkable in enabling useable images at very slow hand hold speeds for the focal length of lens - ie 1/4 to 1/30 range with 50mm on FF. However shake is erratic and the IS is oscillating the lens in compensation - I've found that it is possible to get much sharper images hand held with it turned off at certain speeds in the 1/60 to 1/250 region, but it's random - caveat, this is with 24 - 105 IS system.

And Freelancer - calling someone of RLPhoto's ability a clown makes you the clown pal.

Go look at his work posted on this forum and when yours is half as good you can give yourself a pat on the back

Just thinking of my shooting habits:Anything 50mm and under I turn it off for 1/60 and above, maybe 1/80 depending on many other factors50-100mm I turn it off for 1/80 to 1/100 and above.100-200mm I turn it off for 1/160 and above.

I love IS when I need it, but only when I need it. Any other time it annoys the crap out of me. The sound coming from the lens just does not sound natural.

Hmm... I've never given IS a thought. It just stays on and does what it does. All I ever knew was to turn it off on a tripod but even that isn't an issue with the newer IS as they apparently detect that state and scale back their function automatically. I never considered the possibility of gaining IQ by keeping or turning it off as RLPhoto mentions. Anyone else besides Sporgon and RLPhoto have an educated reason and experience keeping IS off? I may have to try it. I guess the plan for keeping it off is just use it for low light, slower shutter speed and very long reach times? I guess now I'm intrigued that I could get sharper images with IS off and so I'm interested in trying it. My bigger fear is that I'll forget to turn it on when it's really necc.

I still have to think that IS was designed to be left on (not off) and so I wonder how much IQ etc is actually gained by going to the trouble of managing it, manually switching it off and on.

If I shoot things moving in a steady pace and in pretty much one direction, like a runner or a car I keep it on, always. If I shoot hockey or kids or soccer I shoot with only vertical IS on (or off if I'm in portrait mode), that way I can snap the camera back and forth and not see that slight drag/delay in the VF but still have the benefit of some stabilising, absolutely helps predictive AF.

So it's not about shutter speed for me, but how the subject moves.

And as mentioned above here, 1/200s at 200mm rule doesn't work all that well with high mp bodies. I will always use 1600 or 12800 ISO to get fast speed rather than one step cleaner image with slight blur.